Can AWS block access from embargoed countries?
Solution 1:
If you front your website with cloudfront, you could utilize their geo restriction feature. You could also use Route 53's geo DNS feature to null route the traffic.
http://aws.amazon.com/about-aws/whats-new/2013/12/18/amazon-cloudfront-adds-geo-restriction-feature/
http://aws.amazon.com/blogs/aws/route-53-domain-reg-geo-route-price-drop/